Mourners line up to visit the memorial altar in Ansan, Gyeonggi Province, Sunday. The playing field of a neighboring public school was used to accommodate the large number of visitors. (Yonhap)

South Korean authorities on Sunday expanded their probe into the ferry disaster that left more than 300 people dead or missing as search and rescue operations continued at a slow pace off the southern coast.

Since the passenger ferry Sewol sank on April 16, the death toll has climbed to 188, with 114 still unaccounted for, as of 6 p.m. Sunday.

As part of the investigation into the accident, investigators requested search warrants for the Coast Guard in Mokpo, South Jeolla Province, to look into whether the maritime police mishandled its rescue response. Investigators plan to raid the situation room of the Coast Guard on Monday if its warrant is granted by the court.

Prosecutors will also investigate whether the maritime police reacted to the distress call in accordance with its manual and whether their response was appropriate.

Public criticism has mounted over the Coast Guard’s initial response after it was discovered that it had asked a teenage passenger, who first called for help, about the latitude and longitude of the site.

Earlier in the day, prosecutors raided Jeju Vessel Traffic Service and seized communications log and surveillance camera records to look into possibilities of negligence of duties, officials said.

The Jeju VTS was the first service that Sewol crew members contacted for urgent help, a few minutes after passenger’s report to the maritime police. Receiving the report from the ferry crew, the Jeju VTS passed the report to the Jindo VTS as the ferry was within the Jindo VTS control area.

This is the second raid following the Jindo VTS office. On Saturday, the authorities seized communication and phone records that were conducted between the Jindo office and the ferry crew.

The Jindo VTS is accused of neglecting its duties to monitor the ferry in the emergency situation in its control area. It did not acknowledge the situation of the ferry for 18 minutes from the occurrence, investigators said.

Investigators will look into any delays or mishandlings regarding the communication of between the two VTS offices.

While most of the nation’s VTS offices including the Jeju one are under the Oceans and Fisheries Ministy’s control, the Jindo office is under the maritime police’s authority.

The divided control of the VTS offices may have caused some delays in the initial rescue work, critics suspected.

The control was split into two after an oil spill occurred off the west coast near Taean, South Chungcheong Province, in 2007. The Coast Guard requested to the Prime Minister’s Office to have the authority over the VTS offices in coastal areas to enhance its control over ships. The maritime police said the control transfer would help prevent potential oil spills as the maritime police have investigation rights unlike the Oceans Ministry.

In addition to the seizure and search of the VTS offices, prosecutors on Saturday detained four more crew members on charges of abandoning ship without helping passengers evacuate, taking a total 15 crew members into custody. Other members including the captain were arrested earlier.

For the captain, investigators listed five charges including negligence of duty and the violation of the maritime rescue rules. Authorities are reviewing whether a murder charge is applicable for the 69-year-old captain as well, sources said.

The captain ordered passengers to stay in their cabins until the ship regained balance, leaving many to drown, survivors said.

Meanwhile, search and rescue operations made little progress over the weekend due to the bad weather.

The Coast Guard and Navy divers attempted to search the third- and fourth-deck cabins where most of the missing are believed to remain trapped. Operations, however, were suspended around Saturday at midnight for a half day due to strong winds and high currents. High-sea alerts were also issued Sunday.

Floating objects within the hull of the sunken ferry also impeded the divers’ work, delaying the pace of the operations, authorities said.

While the search work was underway, many people nationwide mourned the deaths of the ferry victims.

As of Sunday at noon, more than 130,000 mourners have visited the memorial altar temporarily set up in Ansan, Gyeonggi Province, since last Wednesday.

Funerals of 27 other victims were held at several hospitals in Ansan on Sunday.

Hundreds of citizens joined events commemorating the deaths of the victims.

The Seoul Metropolitan Government on Sunday opened a memorial altar in Seoul Plaza as citizens pointed out the lack of venues to express their condolences outside of Ansan.

A dozen local governments also decided to open regional memorial altars in their cities from Monday.